An oil tanker made a u-turn on a Nakhon Ratchasima road early Wednesday, resulting in a pileup of three passenger vans and a pickup truck that killed six people and injured 13 others, police said.

Police said the accident happened at kilometre marker No 108-109 of the Bangkok-bound Mittraparp Road in Tambon Maklua Mai of Nakhon Ratchasima's Sung None district.

The impact of the chain-reaction crash reduced the front of the vehicles involved into heaps of wreckage.

Police said the u-turn spot was dark, and the three vans and the pickup were driving at high speed. After the first van hit the front of the oil tanker, a second van smashed into the wreckage followed by a third and then the pickup.

Police said the driver of the first van, named as K, was killed along with T, the driver of the second van.

Four passengers in the second van were also killed. Two of them were identified as as S and C. Two female victims were not identified.

Thirteen people were rushed to hospital with injuries.

Police have yet to interrogate the survivors to establish the cause of the accident.